Method for manufacturing semiconductor chip

ABSTRACT

A semiconductor wafer (W) where circuits are formed in the area divided by streets is split into semiconductor chips having individual circuits. By interposing an adhesive sheet, whose adhesive force is lowered by stimulation, between the semiconductor wafer (W) and the support plate ( 13 ), the front side of the semiconductor wafer (W) is adhered to the support plate ( 13 ), thereby exposing the rear face ( 10 ) of the semiconductor wafer (W). The rear face ( 10 ) of the semiconductor wafer (W) with the support plate ( 13 ) is ground. After the grinding is finished, the semiconductor wafer (W) held with the rear face ( 10 ) up is diced into semiconductor chips (C). The adhesive sheet is given stimulus to lower the adhesive force and the semiconductor chips (C) are removed from the support plate ( 13 ). The semiconductor wafer and semiconductor chips are always supported by the support plate, avoiding damage and deformation.

TECHNICAL FIELD

The present invention relates to a method for manufacturingsemiconductor chips in which, in the course of a rear face of asemiconductor wafer being ground followed by dicing to obtainsemiconductor chips, the semiconductor wafer and semiconductor chips areinhibited from being damaged and deformed.

BACKGROUND ART

Semiconductor chips such as ICs and LSIs are formed in such a way thatafter a rear face of a semiconductor wafer W in which in each of anumber of regions C divided by streets S as shown in FIG. 14 a circuitis formed is ground to a desired thickness, the semiconductor wafer isdiced vertically and horizontally along the streets S.

When the rear face is ground, a front face side is held by a grindingmachine; accordingly, in order to protect circuits formed on the frontface, ordinarily a protective tape is stuck to the front face.Furthermore, when in order to make various kinds of electronicinstruments smaller and thinner, a semiconductor wafer W is ground to athickness as thin as for instance 100 μm or less, the groundsemiconductor wafer W becomes soft like paper and difficult to handle.In order to make transport and so on thereafter easier, the front faceof the semiconductor wafer W is stuck to a rigid support plate tosupport the semiconductor wafer W; that is, a device for making thetransport and so on easier is applied.

However, when the semiconductor wafer thinned by the grinding of therear face is diced by use of a dicing machine, the semiconductor waferhas to be peeled off from the support plate and to be stuck to a dicingtape; accordingly, in peeling or sticking, the semiconductor wafer islikely to be damaged. Particularly, in a semiconductor wafer of whichthickness is made extremely thin such as 100 μm or less, or 50 μm orless by grinding, it is extremely difficult to reattach it withoutcausing damage.

Furthermore, in an invention disclosed in, for instance, JP-A 10-284449,the grinding and dicing are performed with a front face of asemiconductor wafer stuck to a holding tape, and accordingly, there isno need of reattaching when switching from grinding to dicing; however,when the semiconductor chips are peeled off from the dicing tape afterthe dicing, the semiconductor chips are likely to be damaged such as bycracking or breaking, deformation and so on.

In this connection, the present invention intends to inhibit thesemiconductor wafer and semiconductor chips from being damaged, deformedand so on when a semiconductor wafer is ground and the semiconductorwafer is diced to manufacture semiconductor chips.

SUMMARY OF INVENTION

The present invention provides a method for manufacturing semiconductorchips which is a dividing method in which a semiconductor wafer on whicha circuit is formed in each of regions divided by streets is dividedinto semiconductor chips for individual circuits, the method includingsteps of: integrating a support plate by sticking a front face of asemiconductor wafer to the support plate with an adhesive sheet of whichadherence decreases owing to stimulation intervened therebetween andwith a rear face of the semiconductor wafer exposed; grinding a rearface of the semiconductor wafer that is integrated with the supportplate; dicing the semiconductor wafer that was ground and is integratedwith the support plate with the rear face directed upward intosemiconductor chips; and applying stimulation to the adhesive sheet tolower the adherence and separating the semiconductor chips from thesupport plate.

The method for manufacturing semiconductor chips additionally includesconditions such as: that a gas-generating agent that generates a gasaccording to the stimulation is contained in the adhesive sheet; thestimulation is UV light and the gas-generating agent generates a gas dueto UV light; in the separating step, only a semiconductor chip that iswanted to be separated from the support plate is irradiated by UV light;an adhesive sheet is formed by providing a gas-generating agent made ofan azo compound in at least one or more kinds of resins selected fromacrylic resins, olefinic resins and polycarbonate base resins; thesupport plate is made of a transparent or translucent material; thesupport plate is made of glass and has a thickness from 0.5 to 2.5 mm;and an outer periphery of the support plate is provided with alignmentmarks that indicate positions of streets.

According to the method for manufacturing semiconductor chips thusconfigured, the semiconductor wafer is stuck to a support plate havinghigh rigidity through an adhesive sheet of which adherence decreasesaccording to the stimulation. In this state, the grinding and dicing areapplied, and thereafter the stimulation is applied to lower theadherence. In this manner, a semiconductor chip is picked up,accordingly, in these steps or during transport between these steps, thesemiconductor wafer or the semiconductor chips can always be stablysupported, the semiconductor chips can be safely and assuredly pickedup, and the semiconductor chips do not undergo damage such as cracking,breaking and the like, and deformation and the like.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing a semiconductor wafer to which thepresent invention is applied;

FIG. 2 is a perspective view showing a step of integrating a supportplate that constitutes the invention;

FIG. 3 is a perspective view showing a state in which the semiconductorwafer and the support plate are integrated;

FIG. 4 is a partly enlarged sectional view showing part of a firstexample of an adhesive sheet;

FIG. 5 is a partly enlarged sectional view showing part of a secondexample of an adhesive sheet;

FIG. 6 is a partly enlarged sectional view showing part of a thirdexample of an adhesive sheet;

FIG. 7 is a perspective view showing an example of a grinding machinethat is used in performing a grinding, step according to the invention;

FIG. 8 is a perspective view showing an example of a dicing machine thatis used in performing a dicing step according to the invention;

FIG. 9 is a perspective view showing a state where all streets in onedirection are cut in the step of dicing;

FIG. 10 is a perspective view showing a state where the streets are cutvertically and horizontally in the step of dicing;

FIG. 11 is a perspective view showing a separation step according to theinvention;

FIG. 12 is an explanatory diagram showing the invention with individualsteps;

FIG. 13 is a perspective view showing a second example of a supportplate; and

FIG. 14 is a plan view showing a semiconductor wafer.

DETAILED DESCRIPTION OF THE INVENTION

As the best mode for carrying out the present invention, a method formanufacturing individual semiconductor chips C by grinding a rear faceof a semiconductor wafer W shown in FIG. 1 and dicing streets Svertically and horizontally will be explained.

In a semiconductor wafer W shown in FIG. 1, a circuit is formed on afront face of each of plural regions divided by streets S. As shown inFIG. 2, in a state where the semiconductor wafer W is turned upside downto direct a rear face 10 upward, the front face of the semiconductorwafer W is stuck, through an adhesive sheet 12, to a support plate 13 tointegrate the wafer W and support plate 13 as shown in FIG. 3 (step ofintegrating a support plate). That is, the front face 11 of thesemiconductor wafer W is stuck to the adhesive sheet 12.

The adhesive sheet 12 has the characteristic that its adherencedecreases upon stimulation. For instance, it may include agas-generating agent that lowers the adherence due to the release of agas from a surface. In this case, as the stimulation, for instance, UVlight is used.

The adhesive sheet 12 may be an adhesive and non-support tape that hasadhesive layers 14 and 15 on both faces like an adhesive sheet 12 ashown in FIG. 4, or a type in which adhesive layers 17 and 18 are formedon both faces of a base material 16 like an adhesive sheet 12 b shown inFIG. 5. Furthermore, like an adhesive sheet 12 c shown in FIG. 6, it maybe an unsupported tape made of only a single adhesive layer 19.

In the case of a type of adhesive sheet where the base material 16 isused, such as the adhesive sheet 12 b shown in FIG. 5, if the adhesivelayer 17 is one for which adherence decreases due to light, the basematerial 16 is preferably one that transmits light or allows light topass through; for instance, sheets made of transparent resins such asacryl, olefin, polycarbonate, vinyl chloride, ABS, polyethyleneterephthalate (PET), nylon, urethane, polyimide and so on, sheets havinga network structure, sheets in which holes are opened and so on can beused.

The adhesive layers 14, 17 and 19 that constitute the adhesive sheets 12a, 12 b and 12 c contain a gas-generating agent that generates a gas dueto the stimulation. As the stimulation, light, heat, ultrasound and soon can be used; among these, light or heat can be preferably used.Furthermore, as the light, UV light, visible light and so on can beused.

As the gas-generating agent, there are no particular restrictions;however, for instance, azo compounds and azide compounds can bepreferably used. The azo compounds include such as2,2′-azobis-(N-butyl-2-methylpropion-amide),2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide},2,2′-azobis{2-methyl-N-[2-(1-hydroxybutyl)]propionamide},2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],2,2′-azobis[N-(2-propenyl)-2-methylpropionamide],2,2′-azobis(N-butyl-2-methyl-propionamide),2,2′-azobis(N-cyclohexyl-2-methylpropionamide),2,2′-azobis[2-(5-methyl-2-imidazoline-2-yl)propane]dihydrochloride,2,2′-azobis[2-(2-imidazoline-2-yl)propane]dihydrochloride,2,2′-azobis[2-(2-imidazoline-2-yl) propane]disulfate-dihydrate,2,2′-azobis[2-(3,4,5,6-tetrahydropyrimidine-2-yl)propane]dihydro-chloride,2,2′-azobis{2-[1-(2-hydroxyethyl)-2-imidazoline-2-yl]propane)dihydro-chloride,2,2′-azobis[2-(2-imidazoline-2-yl)propane],2,2′-azobis(2-methyl-propionamydine)hydrochloride,2,2′-azobis(2-aminopropane)dihydrochloride,2,2′-azobis[N-(2-carboxyacyl)-2-methyl-propionamidine],2,2′-azobis{2-[N-(2-carboxyethyl)amidine]propane},2,2′-azobis(2-methylpropionamideoxime), dimethyl2,2′-azobis(2-methylpropionate), dimethyl 2,2′-azobisisobutylate,4,4′-azobis(4-cyanocarbonic acid), 4,4′-azobis(4-cyanopentanoic acid),2, 2′-azobis(2,4,4-trimethylpentane) and so on. Among the steps formanufacturing a semiconductor wafer, there are steps where the wafer isexposed to high temperatures. For instance, in the step of grinding therear face of the semiconductor wafer, a high temperature is caused owingto the frictional heat; accordingly, among these,2,2′-azobis-(N-butyl-2-methyl-propionamide),2,2′-azobis(N-butyl-2-methylpropionamide) and2,2′-azobis(N-cyclohexyl-2-methylpropionamide) that are high in thethermal decomposition temperature are preferable. These azo compoundsgenerate a nitrogen gas by the stimulation due to light, heat and so on.

Furthermore, as the azide compounds, polymers having an azide group suchas 3-azidemethyl-3-methyloxetane, terephthal azide,p-tert-butylbenzazide, and glycidil azide polymers that are obtained byring-opening polymerization of 3-azidemethyl-3-methyloxetane can beused. These azide compounds generate a nitrogen gas by the stimulationdue to light, heat and impact.

Among these gas-generating agents, the azide compounds are problematicbecause these compounds, even when impact is applied, easily decomposeand release a nitrogen gas, and thus, the handling is difficult.Furthermore, the azide compounds, when the decomposition once starts,induce a chain reaction and explosively release a nitrogen gas and, assuch, cannot be controlled; accordingly, there is another problem inthat, in some cases, the semiconductor wafer is damaged due to theexplosively generated nitrogen gas. From these problems, an amount ofthe azide compound to use is limited.

On the other hand, the azo compounds, different from the azidecompounds, do not generate a gas due to the impact; accordingly, the azocompounds are extremely easy to handle. Furthermore, it is most unlikelyfor the azo compounds to cause a chain reaction and explosively generatea gas; accordingly, the semiconductor wafer will not be damaged. Inaddition, since when light irradiation is interrupted, the gasgeneration can be also interrupted, the azo compounds also have anadvantage in that the adhesiveness can be controlled in accordance withthe applications. Accordingly, the azo compounds can be more preferablyused as the gas-generating agent.

When the gas-generating agent as mentioned above is contained in theadhesive layer 14, 17 or 19, the stimulation applied to the adhesivelayer 14, 17 or 19 causes the gas-generating agent to generate a gas andthereby lower the adherence, resulting in easily peeling thesemiconductor chips afterward.

The gas-generating agent may be dispersed in the adhesive layer 14, 17or 19; however, in that case, since the whole adhesive layer becomes anair bubble generating body, the adhesive layer becomes excessively soft,and there is a likelihood that the adhesive layer cannot be well peeled.Accordingly, the gas-generating agent is preferably contained only in asurface layer portion that is in contact with semiconductor wafer W.When the gas-generating agent is contained in the surface layer portion,a contact area between the adhesive sheet and the semiconductor chip isreduced due to the gas generated from the gas-generating agent, and inaddition the gas at least partially peels the adhesive surface of theadhesive layer off the semiconductor chip and thereby lowers theadherence.

As the method of allowing the gas-generating agent to be contained onlyin a surface layer portion of the adhesive layer 14, 17 or 19, forinstance, a method can be used in which an adhesive containing agas-generating agent is coated on the adhesive layer in a thicknesssubstantially from 1 to 20 μm, or a method can be used in which avolatile liquid containing a gas-generating agent is coated or sprayedon a surface of a previously prepared adhesive layer 14, 17 or 19 touniformly stick the gas-generating agent to the surface of the adhesivelayer, and so on.

In the case of the gas-generating agent being stuck to the surface ofthe adhesive layer, it is preferred to use a gas-generating agent thathas excellent compatibility with the adhesive. That is, when thegas-generating agent is much stuck onto the surface of the adhesivelayer, the adherence is deteriorated; however, when the adhesive and thegas-generating agent are compatible, the adherence does not decreasesince adhered gas-generating agent is absorbed by the adhesive.

Although a thickness of the surface layer portion depends on a thicknessof the adhesive layer, it is preferable to have a thickness of up to 20μm from the surface of the adhesive. Furthermore, the surface portionhere contains a mode where the gas-generating agent uniformly adheres tothe surface of the adhesive and a mode where the gas-generating agentstuck to the surface of the adhesive dissolves compatibly with theadhesive to be absorbed by the adhesive layer.

The adhesive constituting the adhesive layers 14, 17 and 19 ispreferably one for which the elastic modulus rises due to thestimulation. In this case, the stimulation to raise the elastic modulusmay be the same as that to generate a gas from the gas-generating agentor may be different therefrom. The adhesive can be, for instance, aphoto-curing adhesive containing an acrylic acid alkyl ester base and/ormethacrylic acid alkyl ester base polymerizing polymer having a radicalpolymerizing unsaturated bond in a molecule and a radical polymerizingpolyfunctional oligomer or monomer as a primary component, and apolymerization initiator as the need arises; or a thermo-settingadhesive containing an acrylic acid alkyl ester base and/or methacrylicacid alkyl ester base polymerizing polymer that has a radicalpolymerizing unsaturated bond in a molecule and a radical polymerizingpolyfunctional oligomer or monomer as primary component, and a thermalpolymerization initiator.

In the curing type adhesives such as the photo-curing adhesive or thethermosetting adhesive as mentioned above, the whole adhesive layer isuniformly and rapidly polymerized and cross-linked to integrate due toirradiation of light or application of heat, and accordingly, the riseof the elastic modulus due to the polymerization and hardening becomesremarkable, resulting in a large decrease in the adherence. Furthermore,when a gas is generated from the gas-generating agent in a hard curedsubstance, most of the generated gas is released outside, and thereleased gas at least partially peels an adhesion surface between thesemiconductor chip and the adhesive layer to result in lowering of theadhesive force.

The polymerizing polymer can be obtained, for instance, by previouslysynthesizing a (meth)acrylic polymer having a functional group in amolecule (hereinafter referred to as “functional group-containing(meth)acrylic polymer”) and by allowing this to react with a compoundhaving a functional group that reacts with the above functional groupand a radical polymerizing unsaturated bond in a molecule (hereinafterreferred to as “functional group-containing unsaturated compound”). Inthe present specification, the (meth)acryl means acryl or methacryl.

The functional group-containing (meth)acrylic polymer, as a polymer thatis adhesive at room temperature, similarly to the case of general(meth)acrylic polymers, can be obtained by copolymerizing, according toan ordinary method, an acrylic acid alkyl ester and/or methacrylic acidalkyl ester in which an alkyl group usually has from 2 to 18 carbonatoms as a primary monomer, a functional group-containing monomer, andas needs arise other reforming monomer copolymerizable therewith. Aweight average molecular weight of the functional group-containing(meth)acrylic polymer is usually substantially from 200,000 to2,000,000.

The functional group-containing monomer can be, for instance, carboxylgroup-containing monomers such as acrylic acid, methacrylic acid and soon; hydroxyl group-containing monomers such as acrylic acidhydroxyethyl, methacrylic acid hydroxyethyl and so on; epoxygroup-containing monomers such as acrylic acid glycidyl, methacrylicacid glycidyl and so on; isocyanate group-containing monomers such asacrylic acid isocyanateethyl, methacrylic acid isocyanateethyl and soon; and amino group-containing monomers such as acrylic acid aminoethyl,methacrylic acid aminoethyl and so on.

As the copolymerizable other reforming monomers, various kinds ofmonomers can be used that are used in the general (meth)acrylic polymerssuch as vinyl acetate, acrylonitrile, styrene and so on.

As the functional group-containing unsaturated compounds that arereacted with the functional group-containing (meth)acrylic polymers,ones similar to the functional group-containing monomers mentioned abovecan be used in accordance with the functional groups of the functionalgroup-containing (meth)acrylic polymers. For instance, in the case ofthe functional group of the functional group-containing (meth)acrylicpolymer being a carboxyl group, an epoxy group-containing monomer or anisocyanate group-containing monomer is used; in the case of thefunctional group being a hydroxyl group, an isocyanate group-containingmonomer is used; in the case of the functional group being an epoxygroup, a carboxyl group-containing monomer or an amide group-containingmonomer such as acryl amide and so on is used; and in the case of thefunctional group being an amino group, an epoxy group-containing monomeris used.

As the polyfunctional oligomers or monomers, ones having a molecularweight of 10,000 or less are preferable, and ones having a molecularweight of 5000 or less and are 2 at the minimum and 20 at the maximum inthe number of the radical polymerizing unsaturated bonds in the moleculeare more preferable, in order that the three-dimensional networking ofthe adhesive layer due to heating or light irradiation may beeffectively formed. The more preferable polyfunctional oligomers ormonomers like this are, for instance, trimethylolpropane triacrylate,tetramethylolmethane tetraacrylate, penta-erythritol triacrylate,pentaerythritol tetraacrylate, dipentaerythritolmonohydroxy-pentaacrylate, dipentaerythritol hexaacrylate, 1,4-butyleneglycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycoldiacrylate, commercially available oligoester acrylate or methacrylatessimilar to the above. These polyfunctional oligomers or monomers may beused singly or in combinations of two or more kinds.

The photo-polymerization initiators, for instance, are ones that can beactivated by the irradiation of light having a wavelength in the rangeof from 250 to 800 nm. The photo-polymerization initiators like this canbe, for instance, acetophenone derivatives such as methoxyacetophenoneand so on; benzoin ether base compounds such as benzoin propyl ether,benzoin isobutyl ether and so on; kethal derivatives such as benzildimethyl ketal, acetophenone diethyl ketal and so on; phosphine oxidederivatives; and photo-radical polymerization initiators such asbis(η5-cyclopentadienyl) titanocene derivatives, benzophenone, Michler'sketone, chlorothioxanthone, dodecylthioxanthone, dimethylthioxantone,diethylthioxantone, α-hydroxycyclo-hexyl phenyl ketone, 2-hydroxymethylphenyl propane and so on. These photo-polymerization initiators may beused singly or in combinations of two or more kinds.

The thermal polymerization initiators can be ones that are decomposeddue to heat and generate an active radical that initiates polymerizationand hardening. Specifically, these can be for instance, dicumylperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, t-butylhydroperoxide, benzoyl peroxide, cumen hydroperoxide, diisopropylbenzenehydroperoxide, paramenthane hydroperoxide, di-t-butyl peroxide and soon. Among these, in view of high thermal decomposition temperature,cumen hydro peroxide, paramenthane hydroperoxide, di-t-butyl peroxideand so on are preferable. Among these thermal polymerization initiators,ones that are commercially available, though not particularlyrestricted, for instance, Perbutyl D, Perbutyl H, Perbutyl P andPermentha H (all manufactured by NOF Corporation) and so on can bepreferably used. These thermal polymerization initiators may be usedsingly or in combinations of two or more kinds.

To the above curing type adhesives, other than the above components,with an intention of adjusting the cohesive force as the adhesive, asneeds arise, various kinds of polyfunctional compounds that arecompounded to general adhesives such as isocyanate compounds, melaminecompounds, epoxy compounds and so on may be appropriately blended.Furthermore, known additives such as a plasticizer, resin, surfactant,wax, fine particle filler and so on may be blended.

The adhesives constituting the adhesive layer 15 shown in FIG. 4 and theadhesive layer 18 shown in FIG. 5 are stuck to the substrate 13, asshown in FIG. 2, and does not necessarily have the property that theadherence becomes lower owing to the stimulation. However, when there isnecessity of peeling the adhesive sheet 12 off the support plate 13, asexplained above, the adhesive layers 15 and 18 are preferablyconstituted of an adhesive of which adherence is lowered by some kind ofstimulation.

The support plate 13 shown in FIG. 2 is made of a hard member such asglass, metal, hard resin and so on, that is high in rigidity and canstably support the adhered semiconductor wafer W without bending. Forinstance, if the support plate 13 is glass, sufficient rigidity can beobtained when the thickness is in the range of substantially from 0.5 to2.5 mm. Furthermore, if the stimulation is light as explained above,light can be allowed to go through when the support plate 13 isconstituted of a transparent or translucent member. A front face of theglass is preferably smooth so that a flat face may be obtained ongrinding.

A rear face of the semiconductor wafer W stuck through the adhesivesheet 12 and integrated with the support plate 13 is ground by use of agrinding machine 20, for instance, as shown in FIG. 7.

In the grinding machine 20, a wall portion 22 is disposed so as to beerected from an end portion of a base table 21, a pair of rails 23 isdisposed in a vertical direction on an inside face of the wall portion22, and as a support portion 24 slides up and down along the rails 23,grinding means 25 attached to the support portion 24 moves up and down.Furthermore, the base table 21 is provided with a rotatable turntable26. Also, the turntable 26 is provided with a plurality of rotatablechuck tables 27 to hold the semiconductor wafer.

In the grinding means 25, a mounter 29 is fitted at a tip end of aspindle 28 having a shaft center in a vertical direction, a grindingwheel 30 is mounted thereunder, and a grindstone 31 is fixed under thegrinding wheel 30, and therefore, as the spindle 28 rotates thegrindstone 31 rotates.

In grinding the semiconductor wafer W by use of the grinding machine 20,the semiconductor wafer W integrated with the support plate 13 is heldby the chuck table 27 with the support plate 13 directed downward andpositioned immediately below the grinding means 25. That is, a rear face10 of the semiconductor wafer W faces the grindstone 31.

Then, when the spindle 28 is rotated and the grinding means 25 islowered, the grinding wheel 30 rotates with the rotation of the spindle28, and the rotating grindstone 31 comes into contact with thesemiconductor wafer W to apply a pressing force thereon, and thereby therear face 10 is ground by the grindstone 31 to have a desired thickness(grinding step).

Subsequently, the semiconductor wafer W, having undergone the grindingstep and having been formed into a desired thickness, is subjected todicing, for instance, by use of a dicing machine 40 as shown in FIG. 8.

In the dicing machine 40, the ground semiconductor wafer W istransferred in a state integrated with the support plate 13, that is,with the rear face 10 of the semiconductor wafer W directed upward, anda plurality of semiconductor wafers is housed in a cassette 41.

The semiconductor wafer W integrated with the support plate 13 istransferred out of the cassette 41 by a transferring-in-and-out means42, then placed on a temporary storage region 43, and thereafterabsorbed by first transfer means 44 and transferred to a chuck table 45by a swing movement thereof, placed thereon with the support plate 13directed downward (with the rear face of the semiconductor wafer Wdirected upward) and absorbed and held.

Subsequently, the chuck table 45 holding the semiconductor wafer W movesin a +X direction and thereby is positioned immediately below alignmentmeans 46. The alignment means 46 is provided with an infrared camera 47that allows light from the rear face 10 of the semiconductor wafer W totransmit and can detect the streets on the front face thereof. Thealignment means 46, while moving in a Y direction, allows the infraredcamera 47 to transmit an image of the rear face 10 of the semiconductorwafer W held by the support plate 13 and to take an image of the frontface, performs the pattern matching processing between a key patternimage previously stored in a memory or the like and a taken image, andthereby detects streets to be cut.

Cutting means 49 provided with a rotating blade 48 are formed integratedwith the alignment means 46. Furthermore, the rotating blade 48 is thesame in a Y-axis as that of the infrared camera 47. That is, both arelocated on a straight line in an X-axis direction.

Accordingly, when a street is detected by the alignment means 46, thestreet and the rotating blade 48 are automatically aligned in the Y-axisdirection. The chuck table 45 holding the semiconductor wafer Wsupported by the support plate 13 moves further in the +X direction, thecutting means 49 descends with the rotating blade 48 rotating at a highspeed and cuts in the detected street from a side of the rear face 10,and thereby the street is cut.

When the chuck table 45 is reciprocated in the X-axis direction and thecutting means 49 is index-fed by a street separation in the Y-axisdirection, all streets in the same direction can be cut as shown in FIG.9.

Furthermore, when the chuck table 45 is rotated by 90 degree and thecutting is carried out similarly to the above, all the streets are cutand diced and thereby the semiconductor wafer is divided into individualsemiconductor chips as shown in FIG. 10 (dicing step).

Even after the wafer is thus diced, the individual semiconductor chips Care still stuck to the support plate 13, and accordingly it is necessaryto peel the semiconductor chips C off the support plate 13 and pick themup.

A number of semiconductor chips C and the support plate 13 are in onebody owing to the adhesive sheet 12 shown in FIG. 2; and accordingly,the semiconductor chips C are made easily peelable by applying thestimulation to the adhesive sheet 12 to lower the adherence of theadhesive sheet 12.

In the case of the gas-generating agent that generates a gas due to, forinstance, UV light being contained in the adhesive sheet 12, UV light isirradiated from a irradiation portion 50 below the support plate 13 togenerate a gas as shown in FIG. 11, thereby a gas is generated betweenthe semiconductor chips C, and accordingly the adherence can be lowered.

At this time, the UV light can be irradiated to the whole adhesive sheet12. However, when the adherence of the whole sheet 12 is lowered, thereis a likelihood that the semiconductor chips C will become detached andfall before they are picked up. Accordingly, as shown in FIG. 11, it ispreferable to irradiate UV light only on a semiconductor chip that willbe immediately picked up. The semiconductor chips stuck to portionswhere adherence is lowered can be easily separated from the supportplate 13 (separation step).

Furthermore, the whole adhesive sheet 12 may be exposed to UV light toreduce the adherence to a certain degree and thereafter irradiating UVlight to portions to be separated immediately before they are separated.Partial heating may be applied to peel chip by chip.

The above-mentioned method of dividing the semiconductor wafer can beillustrated with the individual steps (A) through (D) in FIG. 12.Firstly, in the step of integrating the support plate (A), thesemiconductor wafer W is stuck to the support plate 13 so that the rearface 10 may be directed upward and held in this state by the chuck table27 of the grinding machine, and the rear face thereof is ground by thegrindstone 31 in the grinding step (B).

Then, in the dicing step (C), the semiconductor wafer W is held by thechuck table 45 of the dicing machine in the state being stuck to thesupport plate 13, and the semiconductor wafer W is diced. Finally, theindividual semiconductor chips formed by the dicing are picked up in theseparation step (D) and removed from the support plate 13.

Since the semiconductor chips C thus manufactured are supported by thesupport plate 13 which is high in rigidity during all of the respectivesteps of grinding, dicing and transferring from the grinding to thedicing, the semiconductor chips do not undergo cracking, chipping,deformation and so on. Accordingly, finally manufactured semiconductorchips are high in quality and the yield is also improved.

In particular, even in the case of a semiconductor wafer having, forinstance, a thickness of 50 μm or less where many of the semiconductorwafers usually undergo damage, deformation and so on in the course ofmanufacture, high-quality semiconductor chips can be manufacturedwithout damage.

In the above mode, infrared light is used to apply alignment in thedicing machine 40; however, when a support plate 51 is made larger thana semiconductor wafer W and alignment marks 53 indicating positions ofstreets are formed in advance on an exposed outer periphery portion 52,as shown in FIG. 13, streets to be cut can be detected to performalignment by imaging the alignment marks 53 according to an ordinaryimaging method without relying on the infrared camera.

INDUSTRIAL APPLICABILITY

As mentioned above, according to the method for manufacturingsemiconductor chips according to the invention, the semiconductor waferis stuck to the highly-rigid support plate through the adhesive sheetfor which adherence decreases due to the stimulation, grinding anddicing are applied in this state, and afterward the stimulation isapplied to lower the adherence, and the semiconductor chips can bepicked up. As a result, in these steps or during transportation betweenthese steps, the semiconductor wafer or semiconductor chips can alwaysbe stably supported and the semiconductor chips can be safely, assuredlyand easily picked up. Accordingly, the present manufacturing method isuseful in manufacturing semiconductor chips having no damage such ascracking and chipping, deformation and so on and are high in quality andyield. In particular, the present invention is extremely useful becauseeven in the case of manufacturing semiconductor chips that are extremelythin in thickness such as 50 μm or less, a similar effect can beobtained.

1. A method for manufacturing semiconductor chips by dividing asemiconductor wafer, on which a circuit is formed in each of pluralregions divided by streets, into semiconductor chips for individualcircuits, said method comprising: integrating a support plate with asemiconductor wafer by sticking a front face of the semiconductor waferto the support plate via an adhesive sheet that includes agas-generating agent which, upon stimulation, generates a gas to loweran adherence of the adhesive sheet; grinding a rear face of thesemiconductor wafer integrated with the support plate; dicing thesemiconductor wafer, ground and integrated with the support plate, fromthe rear face of the semiconductor wafer into semiconductor chips; andseparating the semiconductor chips from the support plate by applyingstimulation to cause generation of gas by the gas-generating agent tolower the adherence of the adhesive sheet.
 2. A method for manufacturingsemiconductor chips according to claim 1, wherein the adhesive sheetincludes the gas-generating agent only in a surface layer portionthereof that is put in contact with the semiconductor wafer when thefront face of the semiconductor wafer is stuck to the support plate,such that the gas-generating agent is not dispersed throughout theadhesive sheet.
 3. A method for manufacturing semiconductor chipsaccording to claim 2, wherein the stimulation is UV light and thegas-generating agent generates a gas due to the UV light.
 4. A methodfor manufacturing semiconductor chips according to claim 3, wherein inthe separating step, only a semiconductor chip that is to be separatedfrom the support plate is irradiated by UV light.
 5. A method formanufacturing semiconductor chips according to claim 3, wherein thegas-generating agent included in the adhesive sheet is made of an azocompound in at least one or more kinds of resins selected from anacrylic, olefinic and polycarbonate base resin.
 6. A method formanufacturing semiconductor chips according to claim 3, wherein thesupport plate is made of a transparent or translucent material.
 7. Amethod for manufacturing semiconductor chips according to claim 3,wherein alignment marks indicating positions of streets are formed on anouter periphery portion of the support plate.
 8. A method formanufacturing semiconductor chips according to claim 1, wherein thestimulation is UV light and the gas-generating agent generates a gas dueto the UV light.
 9. A method for manufacturing semiconductor chipsaccording to claim 8, wherein in the separating step, only asemiconductor chip that is to be separated from the support plate isirradiated by UV light.
 10. A method for manufacturing semiconductorchips according to claim 8, wherein the gas-generating agent included inthe adhesive sheet is made of an azo compound in at least one or morekinds of resins selected from an acrylic, olefinic and polycarbonatebase resin.
 11. A method for manufacturing semiconductor chips accordingto claim 10, wherein the support plate is made of a transparent ortranslucent material.
 12. A method for manufacturing semiconductor chipsaccording to claim 8, wherein alignment marks indicating positions ofstreets are formed on an outer periphery portion of the support plate.13. A method for manufacturing semiconductor chips according to claim 8,wherein the support plate is made of a transparent or translucentmaterial.
 14. A method for manufacturing semiconductor chips accordingto claim 1, wherein the support plate is made of a transparent ortranslucent material.
 15. A method for manufacturing semiconductor chipsaccording to claim 14, wherein the support plate is made of glass and athickness thereof is in the range of from 0.5 to 2.5 mm.
 16. A methodfor manufacturing semiconductor chips according to claim 1, whereinalignment marks indicating positions of streets are formed on an outerperiphery portion of the support plate.